Swift 3 / Why does the snapshot from snapshotView appears blank in iPhone 7 Plus Simulator?

Question

I'm using the following code to create a custom Menu transition. I have spent the last two hours trying to figure out, why the snapshot appears blank (using the iPhone 7 Plus simulator only). But when I wanted to create a video to make it into a gif for this thread, it worked on my iPhone 6S Plus.

Update: Works on iPhone 6S Simulator as well. But still not in 7 Plus.

import UIKit

class PresentMenuAnimator : NSObject {
}

extension PresentMenuAnimator : UIViewControllerAnimatedTransitioning {
    func transitionDuration(using transitionContext: UIViewControllerContextTransitioning?) -> TimeInterval {
        return 0.6
    }

    func animateTransition(using transitionContext: UIViewControllerContextTransitioning) {

        let fromVC = transitionContext.viewController(forKey: UITransitionContextViewControllerKey.from)
        let toVC = transitionContext.viewController(forKey: UITransitionContextViewControllerKey.to)
        let containerView = transitionContext.containerView
        containerView.insertSubview((toVC?.view)!, belowSubview: (fromVC?.view)!)

        // replace main view with snapshot
        let snapshot = fromVC?.view.snapshotView(afterScreenUpdates: false)
        snapshot?.tag = MenuHelper.snapshotNumber
        snapshot?.isUserInteractionEnabled = false
        snapshot?.layer.shadowOpacity = 0.7
        containerView.insertSubview(snapshot!, aboveSubview: (toVC?.view)!)
        fromVC?.view.isHidden = true

        UIView.animate(
            withDuration: transitionDuration(using: transitionContext),
            animations: {
                snapshot!.center.x += UIScreen.main.bounds.width * MenuHelper.menuWidth
            },
            completion: { _ in
                fromVC?.view.isHidden = false
                transitionContext.completeTransition(!transitionContext.transitionWasCancelled)
            }
        )
    }
}

iPhone 6S Plus (physical device) iOS 10

iPhone 7 Plus (simulator) iOS 10

Why is the snapshot on the simulator blank?

GitHub test project

Answer 1

Alternative solution,

Add this UIView extension,

public extension UIView {
    public func snapshotImage() -> UIImage? {
        UIGraphicsBeginImageContextWithOptions(bounds.size, isOpaque, 0)
        drawHierarchy(in: bounds, afterScreenUpdates: false)
        let snapshotImage = UIGraphicsGetImageFromCurrentImageContext()
        UIGraphicsEndImageContext()
        return snapshotImage
    }

    public func snapshotView() -> UIView? {
        if let snapshotImage = snapshotImage() {
            return UIImageView(image: snapshotImage)
        } else {
            return nil
        }
    }
}

Update your following code,

let snapshot = fromVC?.view.snapshotView(afterScreenUpdates: false)

with,

let snapshot = fromVC?.view.snapshotView()

Ref